1. Field of the Invention
The present invention relates to wireless network communications, and more particularly, to a method for communication in a coordinator-based wireless network environment.
2. Description of the Related Art
With the advancement in communication and network technologies, a wired network environment using wired media such as coaxial or optical cables is evolving into a wireless one using wireless signals in various frequency bands. In line with the transition from wired to wireless technology, a computing device that contains a wireless interface module, enables mobility, and performs specific functions by processing various information (“a wireless network device”) is being developed and wireless technologies that enable effective communication between wireless devices on a wireless network are emerging.
There are two major architectures of wireless networks: infrastructure and ad-hoc networks.
The infrastructure network contains an access point (AP) as shown in FIG. 1, whereas the ad-hoc network requires no AP for communication as shown in FIG. 2.
In an infrastructure mode, an AP not only has connectivity to the wired network but also provides communication among wireless network devices within a wireless network. Thus, all data traffic in the infrastructure network is relayed through the AP.
In an ad-hoc mode, wireless network devices within a single wireless network can directly communicate with one another without using an AP.
Such wireless networks can be further classified into two types based on the presence of a coordinator. In one type of network, which is called a “coordinator-based wireless network”, a randomly selected wireless device acts as a coordinator that assigns channel time to other wireless devices within the same wireless network for data transmission, and then the other wireless devices are allowed to transmit data only at the assigned time. As compared to the coordinator-based wireless network, the other type of network allows all network devices to transmit data at any time desired without using a coordinator.
The coordinator-based wireless network is a single independent coordinator-centered network. When there are multiple coordinator-based wireless networks within a certain area, each network has a unique ID to distinguish itself from others.
Thus, while wireless devices can transmit/receive data to/from other network devices during channel time assigned by the coordinator on a coordinator-based network where they belong, they are not allowed to communicate with wireless devices belonging to another coordinator-based network.
For example, as shown in FIG. 3, in a home network system containing three coordinator-based wireless networks 310, 320, and 330, it is assumed that wireless network-1 310, wireless network-2 320, and wireless network-3 330 are built in a first-floor living room, a second-floor schoolroom, and a first-floor bedroom, respectively.
If a user desires to watch movies stored on a media server 315 in the living room using a portable moving picture player 325 in the schoolroom, then the user cannot watch movies since there is no way to communicate between the wireless network-1 310 and the wireless network-2 320. Accordingly, to see the movies, the user has to go downstairs to the living room.
This problem may arise due to restriction on range of radio waves, absence of information on another coordinator-based wireless network, and channel time allocation.
To achieve data transmission and reception between wireless network devices belonging to different coordinator-based wireless networks, a novel network topology needs to be configured. In particular, there is a need for a method for requesting channel time allocation (CTA) in a coordinator-based wireless network to which a wireless network device that receives data belongs. In Wireless Personal Area Networks (WPANs), which are a representative example of a coordinator-based wireless network and comply with the Institute of Electrical and Electronics Engineers (IEEE) 802.15.3 standard, only a wireless network device that desires to transmit data is allowed to request CTA. That is, no network devices that receive or relay data are able to request CTA since they are unaware of information needed for CTA. The IEEE 802.15.3 proposes standards for a PHY layer corresponding to Physical Layer and a Medium Access Control (MAC) layer making up a Data-Link Layer among the seven layers of the Open System Interconnection (OSI) network model developed by the International Organization for Standardization (ISO) for wireless networks.
Thus, in coordinator-based wireless networks such as WPANs, there is a need for a method that allows a wireless network device receiving data to request channel time allocation (CTA).